1. Field of the Invention
The present invention relates to aqueous liquid detergent compositions comprising an alkaline protease and/or one or more other non-proteolytic enzymes, and an enzyme stabilization system. The invention also relates to enhancing stability of the non-proteolytic enzymes in a liquid detergent composition comprising an alkaline protease.
2. Description of Related Art
Proteases have been used in detergent compositions for many years. Aqueous liquid detergent compositions comprising a protease and one or more non-proteolytic enzymes also are well known in the art.
The major problem encountered with such compositions is ensuring a sufficient storage stability of the enzymes in detergent compositions. Enzymes generally denature or degrade in an aqueous medium resulting in a reduction or complete loss of enzyme activity. For example, enzymes can be degraded by other ingredients in a detergent composition, e.g., surfactants and builders. For example, the anionic surfactant sodium dodecylbenzene sulfonate, an effective and inexpensive surfactant, is detrimental to enzyme stability.
In addition, a protease will degrade non-proteolytic enzymes or itself in aqueous liquid detergent compositions. Thus, the residual activity of the non-proteolytic enzymes will rapidly diminish with the storage time of the detergent composition. Attaining stability for both the protease and non-proteolytic enzymes is difficult.
Attempts to improve the stability of enzymes in detergent compositions are known in the art.
U.S. Pat. No. 4,261,868 discloses liquid detergent compositions comprising enzymes and an enzyme stabilizing system comprising (a) 2-25% of a polyfunctional amino compound selected from the group consisting of diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, and tris(hydroxymethyl)aminomethane and (b) 0.25-15% of a boron compound selected from the group consisting of boric acid, boric oxide, borax, and sodium ortho-, meta- or pyroborate.
U.S. Pat. No. 4,318,818 discloses liquid detergent compositions comprising enzymes and an enzyme stabilizing system comprising calcium ion and a low molecular weight carboxylic acid or salt, preferably a formate.
U.S. Pat. No. 5,073,285 discloses a liquid detergent composition comprising a water-insoluble organic peroxy acid, a surfactant, a pH-adjusting jump system which comprises a borate and a polyol, and a stability-enhancing polymer. The detergent composition may further comprise enzymes. The pH jump system provides a suitable pH for the detergent composition and on dilution in the wash, i.e., a low pH of 3-6 during storage to enhance the stability of the organic peroxyacid bleach and a higher pH of 7-9 during washing for bleaching and detergent efficacy.
U.S. Pat. No. 5,733,473 discloses a liquid detergent composition comprising a protease, lipase, and an enzyme stabilization system selected from the group consisting of boric acid, 1,2-propanediol and carboxylic acids, wherein the detergent composition has a pH from 6 to 10.
U.S. Pat. No. 6,624,132 discloses a liquid detergent composition comprising a boric acid salt (e.g., potassium borate) to stabilize one or more enzymes at alkaline pH and a concentration of water of at least 60%.
Crossin (JAOCS 66(7): 1010-1014 (1989)) discloses the use of short chain carboxylic acids such as formic acid for protease stabilization in a high water content, unbuilt liquid detergent composition.
However, there is a need for detergent compositions with improved stability of enzymes in liquid detergent compositions.